Bulk material in waste dumps, silos, portioning hoppers or other storage facilities is used for many different commercial and industrial applications, including the food, chemical, catalyst, raw material and construction material sectors. Such bulk material can accordingly be found in the form of sugar, cereal, rice, flour, granulates, extrudates, sand, gravel or similar materials.
Although such material is not liquid and often gives the impression of being stable and firm, very often it is free-flowing and pourable, thus presenting a movable and unpredictable mass that might bury living beings, in particular humans, as well as objects. In fact, persons working with bulk material are time and again buried under such material and die as a result. They might either sink into the bulk material and/or be buried by an afterflow of bulk material. This is aggravated by the fact that it is not always the entire bulk material in the silo that starts to move in the form of a mass flow, but only a spatially limited part of the bulk material might move (core flow). These dangers may increase due to the formation of bridges and shafts or of bonded or wedged bulk material and the formation of frost funnels or spaces within the bulk material. Persons or larger objects that have sunk into the bulk material usually cannot be pulled out again due to the considerable mass of the bulk material and its potential suction effect, even if they have not yet been completely pulled in. There are frequent reports of desperate attempts to protect persons from being buried by the afterflow of bulk material, which usually involve provisional auxiliary constructs of panels, planks, metal sheets or similar material in order to try to keep the afterflow of bulk material away from the victim. Unfortunately such improvised aids do not always serve their purpose. Often they are not stable enough, cannot be handled correctly under stress or do not allow the necessary adjustments to the spatial conditions of the accident. On the one hand, protective constructions must fit through bulk material containers with often narrow openings, and on the other hand, they must be spatially flexible enough to protect a potentially extensive area from burial, e.g. they must protect a lying, trapped person. A protective device must further be robust and safe, but also reliably manageable under massive stress to provide the protective effect as required in any individual emergency situation.